This invention relates to slide closures for the pouring nozzles of molten metal vessels, and more particularly the invention relates to a rotary slide closure which is designed so that adjustment of the contact pressure between the fixed plate brick and the sliding plate brick and inspection of the slide contacting surfaces of the fixed and sliding plate bricks can be accomplished easily.
Sliding closures have recently been used widely for the purpose of opening and closing the pouring nozzles of vessels for molten metal, such as ladles for molten steel. In other words, it has been the general practice to use a closure comprising a fixed plate brick having a pouring opening and arranged in close contact with the bottom portion of a vessel and a sliding plate brick having at least one opening and pressed against the lower surface of the fixed plate brick to make a rotary or reciprocating motion, whereby the movement of the sliding plate brick brings the opening in the sliding plate brick into and out of alignment with the pouring opening to open and close the vessel pouring nozzle.
An exemplary form of the known rotary type slide closures is shown in FIG. 1.
In the figure, numeral 1 designates the outer shell of a molten metal vessel whose inner surface is lined with a refractory brick 2. An open place is made in the bottom portion of the vessel where a pouring nozzle is to be formed and an upper nozzle brick 3 with an opening 3A is firmly fitted in the bottom opening. A fixed plate support 7 is placed in close contact with the lower surface of the shell 1 so as to enclose the bottom opening. A fixed plate brick 4 is received in the fixed plate support 7 so as to be placed in close contact with the upper nozzle brick 3 with its opening 4A being aligned with the opening 3A. The openings 3A and 4A form the pouring nozzle. Rotatably pressed against the lower surface of the fixed plate brick 4 is a sliding plate brick 5 which is received in a sliding plate support 8 (hereinafter referred to as a rotor). The sliding plate brick 5 is formed with two openings 5A, 5A. A gear 8A is formed on the periphery of the rotor 8 and the gear 8A is rotatable from a driving source which is not shown so as to rotate the sliding plate brick 5 in sliding contact with the fixed plate brick 4. Pouring nozzles 6, 6 are placed in close contact with the lower surface of the sliding plate brick 5 in such a manner that their openings 6A are aligned with the openings 5A and the pouring nozzles 6 are held, along with the sliding plate brick 5, in place by the rotor 8.
The rotor 8 is slidably supported in a frame 10 at a mating surface 9 and the frame 10 is provided with a plurality of spring cases 11 on its peripheral portion.
On the other hand, a bed plate 16 is firmly fastened to the lower surface of the shell 1 so as to surround the pouring opening 3A. A base plate 15 is secured to the bed plate 16 with four bolts 17. As shown in the Figure, the base plate 15 holds the fixed plate support 7 in place and the plate 15 is formed with holes for through-bolts 14 at positions which are in alignment with the tops of the spring cases 11. The bolts 14 which are inserted in the holes and held in place by their heads, are each loosely fitted in one of the spring cases 11. A coil spring 13 is mounted in each spring case 11 to surround the bolt 14. The lower end of the spring 13 is supported by a washer 12 threadedly fitted on the bolt 14. As a result, by fastening the base plate 15 to the bed plate 16, the fixed plate support 7 is held in close contact with the shell 1. By turning the other ends 14A of the bolts 14 with a jig so as to vertically move the washers 12 and thereby to adjust the force of the springs 13, it is possible to obtain the suitable pressure for pressing the fixed and sliding plate bricks 4 and 5 against each other.
The operation of this pouring nozzle closure is as follows. When the rotor 8 is rotated from the driving source, the openings 5A of the sliding plate brick 5 are brought into or out of alignment with the pouring nozzle 3A, 4A to open or close the pouring nozzle. Since the fixed and sliding plate bricks 4 and 5 are pressed against each other with the required contact pressure, there is no danger of the molten steel leaking from their contact surface. However, the slide closure is used with high temperature molten steel of about 1600.degree. C. and consequently its opening and closing operations will eventually become incomplete due to the wear of the fixed and sliding plate bricks. While it is dependent on the properties and use condition of the refractory material for the closure, generally it is necessary to replace the closure with a new one each time the ladle is used 4 to 5 times.
In order to replace the slide closure, the closure is first disconnected with the driving source and then the bolts 17 are removed, thus detaching from the bed plate 16 the base plate 15 which is assembled with the fixed plate brick 4, the fixed plate support 7, the sliding plate brick 5, the rotor 8 and the frame 10. The thus detached assembly is generally called as a cassette.
After the cassette has been removed, the bolts 14 are turned and removed and then the base plate 15 is detached from the cassette. Since this allows the fixed and sliding plate bricks 4 and 5 to be separated from each other, the fixed and sliding plate bricks 4 and 5 are replaced and the pouring nozzles 6 are also replaced in case of necessity. After the bricks requiring replacement have been changed in this way, the cassette is reassembled, the springs 13 are readjusted, the contact pressure between the fixed and sliding plate bricks 4 and 5 are adjusted to the desired value and then the cassette is fixed to the bed plate 16 with the bolts 17. To speed up the replacement operation, it has also been practiced to prepare a separate cassette equipped with new fixed and sliding plate bricks and mount it in place upon removal of the old cassette.
However, the above method of using the closures in cassette form and replacing the old cassette with a new one to speed up the replacement of the fixed and sliding plate bricks, has the disadvantage of requiring much skill and time in assemblying the cassettes. In other words, the operation of compressing the springs 13 to generate the desired uniform pressing force, coupled with the large number of the springs 13, requires much time and skill. Moreover, it is necessary to remove the cassette from the molten metal vessel and replace the worn fixed and sliding plate bricks at another place, and also inspection of the slide contacting surfaces of the fixed and sliding plate bricks requires about the same amount of labor and time as in the case of replacement.
While the rotary type slide closure shown in FIG. 1 has been described as an example of the prior art slide closures, the slide closure of the reciprocating type differs from the rotary type only in that the closure makes a reciprocating motion in place of the rotary motion and consequently the reciprocating type involves the similar disadvantages.